How is the mycobiota established in newborns?

At this time, fungal populations in newborns and their long-term impact on health have been very little studied. In babies aged 0 to 1 month, their characterization shows low diversity and relative stability but site-dependent variations, linked in part to the mode of delivery.

Thanks to technological advances, local microbial populations in humans can be more accurately characterized. Although research principally investigates bacteria, the study of mycobiotas is beginning to expand. It aims to clarify the role of the fungal component of the microbiome in different types of diseases, especially mucosal infections. To add to this body of knowledge, an American team worked specifically with newborns so as to detail the development of the fungal populations of three sites (oral cavity, skin and anus) during the first month of life. A cohort of 17 children in good health were tracked; their mycobiotas were characterized at regular intervals and compared to those of other children based on mode of delivery and to the vaginal and anal fungal communities of their mother.

Similar, stable mycobiotas…

First finding: postpartum colonization was structured around a small number of taxa. Taking all sites together, a maximum of 16 were found, the majority being Candida albicans, Candida tropicalis, Candida parapsilosis, Saccharomyces cerevisiae and Candida orthopsilosis. A small distinction: the anal mycobiota contained more C. albicans and C. parapsilosis than the skin and oral mycobiotas. Second finding: the composition of the mycobiotas proved relatively stable throughout the first month of life, with no sign of increase in diversity or maturation.

… and multiple origins

Third finding: study of the fungal population, unlike that of bacteria, revealed that the mode of delivery only slightly modified the populations found in the child: the skin of children born by vaginal delivery displayed a higher proportion of C. albicans, a dominant taxon in the mother for the two sites analyzed, without increasing the level of similarity between the communities present in the child and their mother. The oral populations of children born by cesarean section displayed a higher proportion of C. orthopsilosis. Finally, comparison with the mothers’ vaginal mycobiotas revealed an expected vertical transmission (especially C. albicans), probably coexisting with a colonization linked to the perinatal environment. These results improve knowledge of the human mycobiome and corroborate recent studies. However, the authors consider that additional larger scale studies are required to better identify the sources and causes of the variability in fungal colonization.

Sources:

T. Ward, M. Dominguez-Bello, T. Heisel, et al. Development of the Human Mycobiome over the First Month of Life and across Body Sites. mSystems 3:e00140-17. https://doi.org/10.1128/mSystems.00140-17